Decrease In Dust Concentration Research Articles

Laboratory Determination of Coal Dust Cleaning Efficacy of a Fibrous Filter for Flooded-Bed Dust Scrubber

Fibrous-type dust filters are used in flooded-bed dust scrubbers to capture dust from underground room and pillar mining atmospheres. They have 10–30 layers of finely woven strands that trap particles through the interception and impaction process. A full-cone water spray is installed upstream of the filter, which floods the screen. A scrubber’s efficacy is usually measured and reported in terms of reduction in gravimetric dust concentration at a known location in a mine. This paper reports the particle-size-dependent dust removal efficiency of a fibrous filter obtained from an instrumented test-set up. A variable frequency drive and an inline flow control knob were used to control the airflow through the filter and water flow onto the filter. Optical particle counting of coal dust particles upstream and downstream was carried out to determine the cleaning efficacy. Experiments showed an increase in cleaning efficiency for all the dust particles with their size. A progressive decrease in dust concentration downstream of the filter with an increase in water flow through the nozzle affirmed the capture of dust particles by water sprays.

Dust Reduction Efficiency of a Single-Row Vegetative Barrier (Maclura pomifera)

Little is known about the dust removal efficiency of common vegetative barriers. This study of blowing dust reduction was conducted on one of the most common vegetative barriers used for wind erosion control in Kansas and the U.S. Great Plains, the deciduous tree species (Osage orange). A dust generator and distributor were fabricated to generate dust particles for determining the dust removal efficiency of a single-row Osage orange barrier. Simultaneous upwind and downwind dust concentrations were measured using mini-vol samplers for total suspended particulates (TSP) at heights of 1.5, 3.0, 4.5, and 6.0 m above the ground. Measurements were made using two towers located at upwind and downwind distances equal to the height of the barrier. Particle size distribution (PSD) analysis of the initial generated dust showed that most particles were large (GMD = 102.8 µm), while about 5% of the dust was particulate matter less than 2.5 µm in diameter (PM2.5) and 15% was less than 10 µm (PM10). Laser diffraction analysis of particles from the sample filters was used to determine the dust reduction efficiency of the barrier. Results showed that dust reduction was significantly related to reduction in wind speed at lower heights, causing an overall decrease in dust concentration as particles passed through the barrier. Concentrations of larger particles (~100 µm) were also reduced relative to smaller particles when dust passed through the barrier. The data also showed that 4.5 m above the ground, near the crown of the canopy, was most efficient at removing the PM2.5 (15% to 54%) and PM10 (23% to 65%) fractions of the generated dust. Keywords: Generated dust, Osage orange, PM2.5, PM10, TSP, Wind erosion.

Aeolian deposits at the southeastern margin of the Tengger Desert (China): Implications for surface wind strength in the Asian dust source area over the past 20,000 years

Independent dust provenance data play an important role in understanding changes in the atmospheric dust loading over geological time. Major elemental compositions and grain-size characteristics of the aeolian deposits (Xiangshan (XS) section) at the southeastern margin of the Tengger Desert in northwestern China demonstrate that the deposits are an intermediate product of the transportation of aeolian materials from the dust source area (deserts) to the dust depositional regions (Chinese Loess Plateau) that were likely formed by dust storm processes. The > 40 μm and 63–178 μm fractions and the ratio of SiO 2/TiO 2 of the XS section were used as proxies to reconstruct the surface wind regime over the last 20 kyr. The results show that the surface winds were much stronger and fluctuate acutely from 19.1 to 11.4 kyr. The winds gradually attenuated after the beginning of the Holocene and reached a minimum between 4.0 and 3.5 kyr BP. A sharp increase in surface winds occurred after 2.5 kyr BP. The surface winds in the Asian dust source area are largely consistent with the changes in winter monsoon strength documented by the Chinese loess deposits. Also, the stronger surface winds from 19.1 to 11.4 kyr coincide with the high mineral dust concentration determined from the Greenland ice core, except for the period of Bölling–Allerød (B/A), when the atmospheric dust may have been washed out by enhanced global hydrological cycles although dust was still emitted from source areas. This suggests that the stronger surface winds in dust source areas can enhance the atmospheric dust loadings during the late glacial. The weakening surface wind regime during the Holocene may have greatly contributed to the decrease in dust concentration of the remote dust records. The paleo-environmental changes in the study area since 42.5 kyr BP are broadly in agreement with other adjacent records. However, the possible warm and humid spell of 42.5–19.1 kyr BP still requires verification.

Determinants of Wood Dust Exposure in the Danish Furniture Industry—Results from Two Cross-Sectional Studies 6 Years Apart

Objectives: This paper investigates determinants of wood dust exposure and trends in dust level in the furniture industry of Viborg County, Denmark, using data from two cross-sectional studies 6 years apart.Methods: During the winter 1997/1998, 54 factories were visited (hereafter study 1). In the winter 2003/2004, 27 factories were revisited, and personal dust measurements were repeated. In addition, 14 new factories were included (hereafter study 2). A total of 2303 woodworkers participated in study 1, and 2358 measurements from 1702 workers were available. From study 2, 1581 woodworkers participated and 1355 measurements from 1044 workers were available. Information on occupational variables describing potential determinants of exposures like work task, exhaust ventilation, enclosure and cleaning procedures were collected. A total of 2627 measurements and 1907 persons were included in the final mixed model in order to explore determinants of exposure and trends in dust level.Results: The overall inhalable wood dust concentration (geometric means (geometric standard deviation)) has decreased from 0.95 mg/m3 (2.05) in study 1 to 0.60 mg/m3 (1.63) in study 2, representing a 7% annual decrease in dust concentration, which was confirmed in the mixed model. From study 1 to study 2 there has been a change towards less manual work and more efficient cleaning methods, but on the contrary also more inadequate exhaust ventilation systems. The following determinants were found to ‘increase’ dust concentration: sanding; use of compressed air; use of full-automatic machines; manual work; cleaning of work pieces with compressed air; kitchen producing factories and small factories (<20 employees). The following determinants of exposure were found to ‘decrease’ dust concentration: manual assembling/packing; sanding with adequate exhaust ventilation; adequate exhaust ventilation; vacuum cleaning of machines and special cleaning staff.Conclusions: Despite a substantial drop in the dust concentration during the last 6 years in the furniture industry in Viborg County, further improvements are possible. There should be more focus on improved exhaust ventilation, professional cleaning methods and avoiding use of compressed air.

Aeolian input of bioavailable iron to the ocean

Atmospheric deposition of mineral dust supplies much of the essential nutrient iron to the ocean. Presumably only the readily soluble fraction is available for biological uptake. Previous ocean models assumed this fraction was constant. Here the variable solubility of Fe in aerosols and precipitation is parameterized with a two‐step mechanism, the development of a sulfate coating followed by the dissolution of iron (hydr)oxide on the dust aerosols. The predicted soluble Fe fraction increases with transport time from the source region and with the corresponding decrease in dust concentration. The soluble fraction is ∼1 percent near sources, but often 10–40 percent farther away producing a significant increase in soluble Fe deposition in remote ocean regions. Our results may require more rapid biological and physicochemical scavenging of Fe than used in current ocean models. We further suggest that increasing SO2 emission alone could have caused significant Fe fertilization in the modern northern hemisphere oceans.